The "X Window System" is a portable software standard developed at the Massachusetts Institute of Technology. It controls the displays of engineering work stations and provides a standard environment to applications software such as page lay-out editors and computer-aided design packages. Applications that use the "X Window System" to operate a workstation display can easily be recompiled and run on a variety of workstations from a variety of computer vendors. The "X Window System" environment has a client process and a server process. The client process typically performs the computations while the server process performs the input/output operations such as graphics display or graphics input. The client and server may be located on the same computer system, however, they may also be located in different computer systems typically connected by a local area network. A server represents the input and output facilities for a single user of the system. A server, in addition to a keyboard and a graphical input device, may have one or more display elements, each of which may have one or more hardware frame buffers wherein each frame buffer maps to a single screen.
If a server has a single display element, the user is limited to the number of windows that can be comfortably operated from such a single display element. If the user wishes to address additional windows in the "X Window System" environment, additional display elements would have to be installed on the server.
Some display servers used with the "X Windows" have multiple hardware frame buffers that serve a single display element. Each of these buffers appears as a separate screen to the "X Window System", and some mechanism is provided to allow the user to switch from displaying one hardware frame buffer to displaying the next.
The "UNIX" operating system sold by the Santa Cruz Operation (SCO) for use on personal computers, allows a limited form of multiple virtual screens for a single display element. In the SCO system, the personal computer keyboard and display can be used to allow multiple users to log-on to the system, or allow a single user to log-on multiple times. By using the function keys on the keyboard of the personal computer, a user can select a new virtual screen which allows the user to log-on again to perform different functions.
There is need in the art for a system which allows multiple virtual screens within the "X Window" environment that would work on a display having a single hardware frame buffer. There is also a need in the art for a system which allows multiple virtual screens within the "X Window" environment that would work on a display having multiple hardware frame buffers. The present invention meets these needs.